1. Field of the Invention
The present invention relates to a bicycle speed control apparatus attached to a handlebar having a grip.
2. Description of the Related Art
A conventional bicycle speed control apparatus has a shift lever pivotable about an axis extending perpendicular to a handlebar axis from a position adjacent the handlebar axis as disclosed in U.S. Pat. Nos. 4,699,018 and 5,052,241, for example. A control knob formed on the shift lever describes a locus of movement between a position close to the handlebar or a grip of the handlebar, and a position remote therefrom. Thus, when the shift lever is operated by the thumb of a hand holding the grip, the thumb moves toward and away from the fingers holding the grip. Where the speed control apparatus is designed to set the control knob at a short distance to the grip when the shift lever is in home position, the thumb operating the shift lever must be stretched to a remote position at the end of a shifting operation. Conversely, where the speed control apparatus is designed to set the control knob at a short distance to the grip when the shift lever is at an end of its shifting range, the thumb used to operate the shift lever must be stretched to a remote position at the beginning of a shifting operation.
As a further point to be considered, since the distance between the thumb operating the shift lever and the fingers holding the grip is variable, it may be difficult to operate the shift lever with the thumb alone. The shift lever may have to be operated in one direction with the first finger and in the other direction with the thumb. In such a case, a shifting operation requires use of the thumb and one finger, leaving the remaining three fingers to hold the grip of the handlebar, which results in riding instability. It is still more difficult to carry out a shifting operation while applying the brake.